December 20, 2012

Eric Massey

ADEQ, Air Quality

Dear Mr. Massey.

Your exceptional event documentation for July 3, 2011 was reviewed at the NRCD meeting today Dec.

20, 2012

Thank you for your work on this report. It does show the exceptional event that happened July 3, 2011.

We appreciate tha t you have made this statement for Yuma County.

Unfortunately this is not the only exceptional event that has happened. We had another storm this last

summer that took out trees and did more that move PM10.

We look forward to our continued conservation about air quality and the effects of hu midity,

temperature, and desert soils on air quality. As you know Yuma County and the agricultural community

would like to become an attainment area.

Thank you for all of your work collecting data to make these demonstrations.

Yours truly,

Mark Kuechel

Yuma NRCD

Sheryl Christenson

Laguna NRCDSouthern Regional Office

400 West Congress Street  Suite 433  Tucson, AZ 85701

(520) 628-6733

Printed on rec January 25, 2013

Joy E. Herr-Cardillo

Arizona Center for Law in the Public Interest 2205 E. Speedway Blvd

Tucson, AZ 85719

RE: Response Submitted on January 1, 2013 to ADEQ Concerning the Request for Public Comments on the Exceptional Event Demonstrat ion Packages for the Greater Phoenix Area

Posted on December 3, 2012.

Dear Ms. Herr-Cardillo;

Thank you for reviewing and providing comments to these exceptional even t demonstrations. We agree that ADEQ’s highest priority is to pr otect public health. Collectively, we have made great strides in improving the leve ls of PM10 in Maricopa County.

Recently, we published our 25 th Anniversary report. This repor t shows that the PM10 trend in Maricopa County has decreased by 40% over the last two decades due to the implementations of numerous control measures and cooperation with other air quality agencies and stakeholders.

http://www.azdeq.gov/function/about/download/25th_anniversary_book-web.pdf

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Your letter also mentioned the study carri ed out by ASU, ADHS and ADEQ on PM10

concentrations and asthma incidences. One of the recommendations, Chapter 8 Asthma Warning System, recommended ADEQ adop t a two part program; a pred ictive air pollution forecast system and an automated communications netw ork that would advise the news media and citizens via phone, text and/or emai l with the daily air quality for ecast. ADEQ has done just that and provides forecasts to Maricopa County (and products to Yuma, Noga les and Green Valley). We coordinate with Maricopa County’s Clean Air Make More, so that the ADEQ forecasts go directly to their website and subs cribers, as well. Now, more than ever, citizens, mothers of asthmatic children, school nurses, or other school officials can get accurate and timely air quality forecast information sent directly to them on a daily basis. To subscribe go to:

https://public.govdelivery.com/accounts/AZDEQ/subscriber/new

ADEQ has also implemented an Air Quality Flag program that can be used by schools to provide a visual indication of the air quality forecas t to students, faculty and local residents.

http://www.azdeq.gov/ceh/flag.html

Additionally, ADEQ’s Air Quality program adheres to the principles of ensuring conformity with EPA and ADEQ quality assurance programs, and submittal of the ambient air monitoring data to the Federal air quality database that is accessible to the public.

The point of the exceptional event ru le is to provide a means to carefully screen air quality data

to ensure that events that overwhelm reasonabl e controls are accurate ly represented in all monitoring data and analysis. Fo r the exceptional event days, these data are flagged in the EPA database. The exceptional event demonstrations provide EPA with an analysis and seek EPA’s

concurrence that these events overwhelmed Best Available Control Measures (BACM) and Most Stringent Measures (MSM) already in place and that the exceedances are due to exceptional events that were beyond establishe d controls at the time of the ev ent. These demonstrations were prepared following the EPA guidance. They demons trate that these events met the definition and

criteria for exclusion as a llowed in the Exceptional Event Rule, 40 CFR Parts 50 and 51.

Attached are more specific responses to your comment s. We appreciate your participation in this process and join you in the commitment to continue to protect public health for the citizens of

Arizona.

Sincerely,

Eric C. Massey, Director Air Quality DivisionComment 1

Comment: The demonstrations did not provide a reasonable degree of transparency about analytical methods so that independe nt reanalysis coul d be undertaken.

Response: These demonstrations include a de scription of analytical method, specifically those including time series geographic informa tion system (GIS) analysis. All other data included constitutes hourly average time seri es plots obtained from EPA’s Air Quality System (AQS) database or operating agency.

EPA quality assurance procedures were followed with collection of all state and local

ambient data included in the demonstrati on. ADEQ relies on National Weather Service (NWS) quality systems for meteorological data.

ADEQ has the videos available to the public upon request in the ev ent that a user is unable to open a link in the document. ADEQ ha s verified function of all video web links with the exception of one. The links provided in the August 25 through 28, 2011

demonstration were incorrect and have been corrected in the fina l version. ADEQ has the videos available to the public upon request. The compression method used to create the videos aimed to provide both the best resolu tion possible and minimize file size so that users can readily obtain the files.

ADEQ reviewed the draft documents and found two documents containing the statement that “additional documentation may be provided at a later date”. The statement refers to

exceedances recorded outside of the Marico pa County non-attainment area, specifically Pinal County, during the same time period and further explains that theses exceedances may be addressed in a separate exceptional ev ent submittal in the future and will be made available for public review at that time.

ADEQ reviewed the comment and no additi onal changes to the demonstration are

necessary.

Comment 2

Comment: The demonstrations should be tested by modeling.

Response: The exceptional event demonstra tions rely on actual measured values including, particulate con centration and meteorological parameters. EPA guidance recommends that the agency use actual measured data to perform a demonstration that the events were exceptional in nature. Th e addition of model de rived data into the analysis would not provide additional benef it in characterizing the events. Models are generally used to predict a future occurrence rather while actual measured data represent

what did occur. Dust models, like those liste d by the commenter, have not historically been capable of reproducing ac tual measured particulate co ncentrations and should be reserved for predictive exercises such as dust forecasting. ADEQ was unable to find the referenced modeling data on the commenter’s website and, ther efore, is unable to providefurther comment on its use. ADEQ reviewed the comment and no additional changes to the demonstration are necessary.

Comment 3

Comment: The historical fluctuations are oversimplified.

Response: The historical fluctuation analysis conducted for these demonstrations meet recommendations in the latest EPA guidance and have been approved as an appropriate method in past exceptional event requests submitted by ADEQ. The purpose of the historical analysis is to provide a comparison of the requested exceptional event day to past measurements. Its purpose is not to attempt to determine potential contributing sources on the exceedance day. The Conceptual Model and Clear Causal Relationship sections of the demonstration provide an explanation of the conditions during the event. ADEQ has

determined that the Historical Fluctuation s ection clearly represents the specific exceedance day in the context of past measurements. ADEQ reviewed the comment and no additional changes to the demonstration are necessary.

Comment 4

1 st paragraph relating to the July 18, 2011 demonstration and timing of the South Phoenix

winds, 17:50 arrival time of dust at South P hoenix and modeled surface friction velocity.

Response: ADEQ is unable to verify the comm enter’s suggestion that the demonstration specifies the impact at the South Phoenix m onitor occurred precisely at 17:50. The South Phoenix site recorded a maximum hourly PM10 concentration of 2861μg/m3 during the 1800 hour which corresponds to area maximum particulate concentr ations provided in

Table 5-2. The table illustrates area-wide PM10 concentrations, Sky Harbor winds and visibility. The plot clearly shows a wi nd speed increase between 1700 and 1800 and a corresponding PM10 increase and visibility decr ease. The radar derived proximity of the storm cell to the Phoenix area, approximatel y 25 miles south south-east as noted by the commenter, is not a clear indicator of the posi tion of the storm outflow. In this event the

outflow arrived ahead of the thunderstorm as evident in the details provided in the exceptional event demonstration. ADEQ re viewed the comment and no additional changes to the demonstration are necessary.

2 nd paragraph relating to the met hod of subtracting the Glendale monitor value from the South Phoenix value and sugges tion that Glendale represents overall dust storm impacts.

Response: The process of subtracting one area monitor from another is not an appropriate methodology for evaluating region-wide dust storm events. Further, ADEQ disagrees that the Glendale site represents overall dust stor m impacts. The impact of the outflow dust is evident at nearly all Phoeni x area PM10 monitors although the magnitude varies from site to site. This variability is descri bed in the exceptional event document and is attributed to an influx of particulate matte r from outside the non-attainment boundary and

the contribution of local sources where local controls were overwhelmed. ADEQ

reviewed the comment and no additional cha nges to the demonstration are necessary.3 rd paragraph relating to the arri val of dust impacts at South Phoenix at 17:50, local dust sources already increasing PM10 ant South P hoenix but not Glendale, and video of dust

devils at South Phoe nix well before 17:50.

Response: ADEQ is unable to verify the comm enter’s suggestion that the demonstration specifies the impact at the South Phoenix monitor occurred precisely at 17:50. The visibility videos show, as do hourly measur ements, an earlier, less intense, dust cloud moving through the area at approximately 1600 and 1700. ADEQ reviewed the comment and no additional changes to the demonstration are necessary.

4 th paragraph relating to ADEQ’s claims that the Buckeye exceedance is very rare and in the 99.5 percentile while 10 other values ar e above 99.5 percentile (9 during summer months 1 in November).

Response: This is the purpose of the historical fluctuations analysis, to provide the past maximum PM10 data so this event can be compar ed to the historical record and show the

extent to which it varies from the norm. ADEQ reviewed the comment and no additional changes to the demonstration are necessary.

Comment 5

Comment: The August 25, 2011 through August 28, 2011 demonstrations rely on recorded wind speeds of 30 mph at Mesa Williams airport (p. 40), however these data are marked as suspect by NCDC.

Response: The data does have an “s” flag. Bu t it does not mean the value is erroneous.

According to Appendix L: Hourly Data Quality Control Document, of the NCDC Technical Document, one test as a part of the automated QA/QC process involves a “check to see if the wind speed has increased or decreased by more that 20 knots from the average of previous and following hourly observa tions”. If the change is greater than 20 knots, a flag will be placed on the data. We be lieve this is what occurred in reference to the “s” flag placed on the 30 mph reading at the Mesa Williams airport station. A wind speed of 5 mph was recorded before and 9 mph was recorded after the 30 mph reading. The suspect flag was likely placed on the da ta as part of the automated QA/QC process due to the sudden onset, and subsequent s udden decrease, in winds. Such sudden wind increases are not uncommon during the Ar izona Monsoon due to the generation and propagation of outflow boundari es. These outflows can cause sudden increases in winds that can be very short lived, which would account for the short-term high wind reading and subsequent data flag. Add itional high winds were reported in other parts of Maricopa and Pinal Counties including upwind at Casa Grande Municipal Airport, which saw sustained winds above 20 mph with gusts to 25 mph within the hour of, but preceding, the 30 mph report at Mesa Williams. Th e NCDC QA Rules Effective January, 2005 state:1) flags will be available for most data elements if data are suspect, 2) ‘s” will be appended to the value on the web form or in a column following the suspect value in theASCII form, and 3) if data are flagged as erroneous, it will not be printed. ADEQ

reviewed the comment and no additional cha nges to the demonstration are necessary.

Comment 6

Comment: The public notice period is inadequate.

Response: There is no specific timeframe pr ovided in the Exceptional Event Rule, 40 CFR 50.14(c)(3), only that an opportunity is provided for public comment.

Submission of demonstrations .(i) A State that has flagged data as being due to an exceptional event and is requesting exclusion of the affected measurement data shall, after no tice and opportunity for public comment, submit a demonstration to justify data exclusion to EPA. ADEQ typically provides a 30 day comment peri od from the public for review of data and proposed actions by ADEQ, which was done for these demonstrations.